Methods and devices for treating fractured and/or diseased bone

ABSTRACT

The present invention relates to devices and methods for treating fractured and/or diseased bone. More specifically, the present invention relates to devices and methods for repairing, reinforcing and/or treating fractured and/or diseased bone using various devices, including cavity-forming devices.

RELATED APPLICATIONS

This is a divisional application of co-pending U.S. application Ser. No.09/827,260 filed 5 Apr. 2001, which claims the benefit of provisionalApplication Ser. No. 60/194,685 filed 5 Apr. 2000, and which is also acontinuation-in-part of application Ser. No. 09/134,323 filed 14 Aug.1998, now U.S. Pat. No. 6,241,734.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to devices and methods for treatingfractured and/or diseased bone. More specifically, the present inventionrelates to devices and methods for repairing, reinforcing and/ortreating fractured and/or diseased bone using various devices, includingcavity-forming devices.

2. Description of the Background

Normal healthy bone is composed of a framework made of proteins,collagen and calcium salts. Healthy bone is typically strong enough towithstand the various stresses experienced by an individual during hisor her normal daily activities, and can normally withstand much greaterstresses for varying lengths of time before failing. However,osteoporosis or a host of other diseases, including such diseases asbreast cancer, hemangiomas, osteolytic metastases or spinal myelomalesions, as well as the long term excessive use of alcohol, tobaccoand/or various drugs, can affect and significantly weaken healthy boneover time. If unchecked, such factors can degrade bone strength to apoint where the bone is especially prone to fracture, collapse and/or isunable to withstand even normal daily stresses.

Unfortunately, losses in bone strength are often difficult to discoveruntil bone integrity has already been seriously compromised. Forinstance, the effects of osteoporosis are often not discovered untilafter a bone fracture has already occurred, at which time much of thepatient's overall bone strength has typically weakened to dangerouslevels. Moreover, as most bone development occurs primarily duringchildhood and early adulthood, long-term losses in bone strength aretypically irreversible. In addition, many bone diseases, includingosteoporosis, cancer, and other bone-related disorders, are notroutinely curable at our current stage of medical development.

For many individuals in our aging world population, undiagnosed and/oruntreatable bone strength losses have already weakened theseindividuals' bones to a point that even normal daily activities pose asignificant threat of fracture. For example, when the bones of the spineare sufficiently weakened, the compressive forces in the spine can oftencause fracture and/or deformation of the vertebral bodies. Forsufficiently weakened bone, even normal daily activities like walkingdown steps or carrying groceries can cause a collapse of one or morespinal bones, much like a piece of chalk collapses under the compressiveweight of a human foot. A fracture of the vertebral body in this manneris typically referred to as a vertebral compression fracture.Researchers estimate that at least 25 percent of all women, and asomewhat smaller percentage of men, over the age of 50 will suffer oneor more vertebral compression fractures due to osteoporosis alone. Inthe United States, it is estimated that over 700,000 vertebralcompression fractures occur each year, over 200,000 of which requiresome form of hospitalization. Other commonly occurring fracturesresulting from weakened bones can include hip, wrist, knee and anklefractures, to name a few.

Fractures such as vertebral compression fractures often result inepisodes of pain that are chronic and intense. Aside from the paincaused by the fracture itself, the involvement of the spinal column canresult in pinched and/or damaged nerves, causing paralysis, loss offunction, and intense pain which radiates throughout the patient's body.Even where nerves are not affected, however, the intense pain associatedwith all types of fractures is debilitating, resulting in a great dealof stress, impaired mobility and other long-term consequences. Forexample, progressive spinal fractures can, over time, cause seriousdeformation of the spine (“kyphosis”), giving an individual ahunched-back appearance, and can also result in significantly reducedlung capacity and increased mortality.

Until recently, treatment options for vertebral compression fractures,as well as other serious fractures and/or losses in bone strength, wereextremely limited—mainly pain management with strong oral or intravenousmedications, reduced activity, bracing and/or radiation therapy, allwith mediocre results. Because patients with these problems aretypically older, and often suffer from various other significant healthcomplications, many of these individuals are unable to tolerate invasivesurgery. In addition, to curb further loss of bone strength, manypatients are given hormones and/or vitamin/mineral supplements—againwith mediocre results and often with significant side effects.

Over the past decade, a technique called vertebroplasty has beenintroduced into the United States. Vertebroplasty involves the injectionof a flowable reinforcing material, usually polymethylmethacrylate(PMMA—commonly known as bone cement), into a fractured, weakened, ordiseased vertebral body. Shortly after injection, the liquid fillingmaterial hardens or polymerizes, desirably supporting the vertebral bodyinternally, alleviating pain and preventing further collapse of theinjected vertebral body.

While vertebroplasty has been shown to reduce some pain associated withvertebral compression fractures, this procedure has certain inherentdrawbacks. The most significant danger associated with vertebroplasty isthe inability of the practitioner to control the flow of liquid bonecement during injection into a vertebral body. Although the location andflow patterns of the cement can be monitored by CT scanning or x-rayfluoroscopy, once the liquid cement exits the injection needle, itnaturally follows the path of least resistance within the bone, which isoften through the cracks and/or gaps in the cancellous and/or corticalbone. Moreover, because the cancellous bone resists the injection of thebone cement and small diameter needles are typically used invertebroplasty procedures, extremely high pressures are required toforce the bone cement through the needle and into the vertebral body.Bone cement, which is viscous, is difficult to inject through smalldiameter needles, and thus many practitioners choose to “thin out” thecement mixture to improve cement injection, which ultimately exacerbatesthe leakage problems. In a recent study where 37 patients with bonemetastases or multiple myeloma were treated with vertebroplasty, 72.5%of the procedures resulted in leakage of the cement outside thevertebral body. Cortet B. et al., Percutaneous Vertebroplasty inPatients With Osteolytic Metastases or Multiple Myeloma (1998).Moreover, where the practitioner attempts to “thin out” the cement byadding additional liquid monomer to the cement mix, the amount ofunpolymerized or “free” monomer increases, which can ultimately be toxicto the patient.

Another drawback of vertebroplasty is due to the inability to visualize(using CT scanning or x-ray fluoroscopy) the various venous and othersoft tissue structures existent within the vertebra. While the positionof the needle within the vertebral body is typically visualized, thelocation of the venous structures within the vertebral body are not.Accordingly, a small diameter vertebroplasty needle can easily beaccidentally positioned within a vein in the vertebral body, and liquidcement pumped directly into the venous system, where the cement easilypasses out the anterior and/or posterior walls of the vertebrae throughthe anterior external venous plexus or the basivertebral vein.

Another significant drawback inherent in vertebroplasty is the inabilityof this procedure to restore the vertebral body to a pre-fracturedcondition prior to the injection of the reinforcing material. Becausethe bone is fractured and/or deformed, and not repositioned prior to theinjection of cement, vertebroplasty essentially “freezes” the bone inits fractured condition. Moreover, it is highly unlikely that atraditional vertebroplasty procedure could be capable of restoringsignificant pre-fracture anatomy—because bone cement flows towards thepath of least resistance, any en-masse movement of the cortical bonewould likely create gaps in the interior and/or walls of the vertebralbody through which the bone cement would then immediately flow.

A more recently developed procedure for treating fractures such asvertebral compression fractures and other bone-related disorders isknown as Kyphoplasty™. See, for example, U.S. Pat. Nos. 4,969,888 and5,108,404. In Kyphoplasty, an expandable body is inserted through asmall opening in the fractured or weakened bone, and then expandedwithin the bone. This procedure compresses the cancellous bone, anddesirably moves the fractured bone to its pre-fractured orientation,creating a cavity within the bone that can be filled with a settablematerial such as cement or any number of synthetic bone substitutes. Ineffect, the procedure “sets” the bone at or near its pre-fractureposition and creates an internal “cast,” protecting the bone fromfurther fracture and/or collapse. This procedure is of course suitablefor use in various other bones as well.

While Kyphoplasty can restore bones to a pre-fractured condition, andinjected bone filler is less likely to leak out of the vertebral bodyduring a Kyphoplasty procedure, Kyphoplasty requires a greater number ofsurgical tools than a vertebroplasty procedure, at an increased cost.Moreover, Kyphoplasty tools are typically larger in diameter thanvertebroplasty tools, and thus require larger incisions and aregenerally more invasive.

SUMMARY OF THE INVENTION

The present invention overcomes many of the problems and disadvantagesassociated with current strategies and designs in medical procedures torepair, reinforce and/or treat weakened, diseased and/or fractured bone.In one preferred embodiment, the present invention relates to improvedvertebroplasty procedures and surgical instruments which facilitate suchprocedures.

In a general embodiment of the method of the present invention, aninsertion device, preferably an eleven gauge spinal needle assembly, isinserted into a targeted vertebral body using fluoroscopic x-ray tomonitor the positioning of the needle. A cavity-forming device isinserted through the needle into the vertebral body. The cavity-formingdevice desirably compresses cancellous bone in the vicinity of thedistal tip of the needle—forming a small cavity within the bone. Thecavity-forming device is removed and cement is introduced through thespinal needle. Bone filler such as bone cement mixed with a fluoroscopicagent is injected into the cavity using x-ray fluoroscopy to monitor theflow of the bone filler within the vertebral body. Bone fillerintroduction is halted when a desired fill amount is reached, thefractured portions of the vertebral body approach and/or return to theirpre-fractured position, or bone filler leakage is imminent. Because acavity is created within the vertebral body prior to bone fillerintroduction, very low injection pressures can be used, significantlyreducing the possibility of cement leakage. In addition, the creation ofdesired flowpaths permits a greater control in the placement of the bonefiller material within the vertebral body.

In another general embodiment of a method of the present invention, aninsertion device, such as a commercially available spinal needleassembly, is inserted through a cortical bone region and into acancellous bone region of a targeted bone using fluoroscopic x-ray tomonitor the positioning of the needle. A first material, such as a bonefiller, is introduced into the cancellous bone region through theinsertion device. An expandable structure is then inserted through theinsertion device and expanded in the bone, compressing the firstmaterial and/or cancellous bone, thereby creating a cavity and/or abarrier region of compressed cancellous bone substantially surroundingthe cavity. A second material, which may be of the same material as thefirst material, is then introduced through the insertion device into thebone. If desired, the first material can comprise a material havingsufficient strength to support the cavity during the surgical procedure,thereby preventing collapse of the cavity upon contraction and removalof the expandable structure. Such first material could include, but isnot limited to, bone cement, bone graft material or metallic andnonmetallic stents.

In a further embodiment, the methods of the present invention areperformed on a compressed and/or fractured vertebra to strengthen thevertebra, returning it, at least partially, to its pre-fracturedposition, protect the vertebra from further fracture or collapse, and/oralleviate the pain associated with spinal fractures and compressions.

In one embodiment of the present invention, a cavity-forming devicecomprises a balloon catheter. The balloon catheter desirablyincorporates a hollow tube which extends through a balloon material. Atthe proximal end of the catheter, the tube and expandable structure areconnected to a fitting. At the distal end, the expandable structure issecured directly to and/or around the hollow tube. The distal end of theexpandable structure and the distal end of the hollow tube are sealed.Near the distal end of the hollow tube are one or more openings throughwhich an inflation medium passes in and out of the hollow tube to expandand contract the expandable structure.

The balloon catheter of the present invention may be inserted through aninsertion device, such as an eleven gauge needle assembly, into a bone,such as a vertebral body, with the distal end of the catheter extendingbeyond the needle to a length determined by the physician. When thecatheter is filled with an inflation medium, the portion of the catheterextending beyond the needle expands outward, compressing cancellous boneand forming a desired cavity within the vertebral body.

In another embodiment of the present invention, the cavity-formingdevice comprises a shaft incorporating one or more wires or “bristles”at the distal end. The cavity-forming device is desirably insertedthrough an insertion device, such as a spinal needle, into a cancellousregion of a bone, such as a vertebral body. As the bristles enter thevertebral body, they displace cancellous bone in a controlled manner,creating one or more small pathways or cavities in the cancellous bone.The cavity-forming device is removed from the vertebral body and needle,and bone filler is introduced into the vertebral body. The bone filler,which normally flows towards the path of least resistance, willinitially flow through the small cavities. If desired, the physician caninterrupt introduction of bone filler and create additional cavities byreinserting the cavity-forming device. By creating desired pathwaysthrough cancellous bone, the present invention reduces opportunities forcement leakage outside of the vertebral body and/or improvesdistribution of bone filler through a significant portion of thevertebral body.

Other objects, advantages, and embodiments of the invention are setforth in part in the description which follows, and in part, will beobvious from this description, or may be learned from the practice ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a spine with a compression fracture in onevertebrae;

FIG. 2 is a diagram of a patient about to undergo surgery;

FIG. 3 is a lateral view, partially broken away and in section, of alumbar vertebra depicting a compression fracture;

FIG. 4 is a coronal view of a lumbar vertebra;

FIG. 5A is a lateral view of a lumbar vertebra depicting a spinal needleinserted into the vertebral body;

FIG. 5B is a lateral view of the lumbar vertebra of FIG. 5A, with thestylet removed from the spinal needle;

FIG. 5C is a lateral view of the lumbar vertebra of FIG. 5B, with acavity-forming device constructed in accordance with one embodiment ofthe present invention inserted into the vertebral body;

FIG. 5D is a lateral view of the lumbar vertebra of FIG. 5C, with thecavity-forming device inflated;

FIG. 5E is a lateral view of the lumbar vertebra of FIG. 5D, with thecavity-forming device deflated;

FIG. 5F is a lateral view of the lumbar vertebra of FIG. 5E, with thecavity-forming device removed from the vertebral body;

FIG. 5G is a lateral view of the lumbar vertebra of FIG. 5F, with a bonefiller injected into the vertebral body;

FIG. 5H is a lateral view of the lumbar vertebra of FIG. 5G, with thespinal needle advanced into the cavity;

FIG. 5I is a lateral view of the lumbar vertebra of FIG. 5H, with asecond bone filler injected into the vertebral body;

FIG. 5J is a lateral view of the lumbar vertebra of FIG. 5I, withadditional bone filler injected into the vertebral body;

FIG. 5K is a lateral view of the lumbar vertebra of FIG. 5J, withadditional bone filler injected into the vertebral body;

FIG. 5L is a lateral view of the lumbar vertebra of FIG. 5K, with thespinal needle removed from vertebral body;

FIG. 6A is a side view of a cavity-forming device constructed inaccordance with an alternate embodiment of the present invention;

FIG. 6B is a close-up view of the distal end of the cavity-formingdevice of FIG. 6A;

FIG. 7A is a lateral view of a lumbar vertebra, depicting thecavity-forming device of FIG. 6A being inserted into the vertebra;

FIG. 7B is a lateral view of the lumbar vertebra of FIG. 7A, with thecavity-forming device deployed within the vertebra;

FIG. 7C is a lateral view of the lumbar vertebra of FIG. 7B, with thecavity-forming device withdrawn from the vertebra;

FIG. 8A is a lateral view of a lumbar vertebra, depicting an alternateprocedure for treating a vertebral body in accordance with the teachingsof the present invention;

FIG. 8B is a lateral view of the lumbar vertebra of FIG. 8A, with acavity-forming device inserted into the bone filler;

FIG. 8C is a lateral view of the lumbar vertebra of FIG. 8B, with thecavity-forming device expanded in the cavity;

FIG. 9 is a side view of a cavity-forming device constructed inaccordance with one embodiment of the present invention;

FIG. 10 is a close-up view of the distal end of a cavity-forming deviceof FIG. 9;

FIG. 11 is a close-up view of the distal end of a balloon catheterprotruding from the distal end of a needle, depicting the inflation ofthe balloon material with an inflation medium;

FIG. 12 is a side view of a cavity-forming device constructed inaccordance with an alternate embodiment of the present invention;

FIG. 13 is a side view of a cavity-forming device constructed inaccordance with another alternate embodiment of the present invention;

FIG. 14 is a side view of a cavity-forming device constructed inaccordance with another alternate embodiment of the present invention;

FIG. 15 is a side view of a cavity-forming device constructed inaccordance with another alternate embodiment of the present invention;

FIG. 16A is a lateral view of a lumbar vertebra, depicting an alternateprocedure for treating a vertebral body in accordance with the teachingsof the present invention;

FIG. 16B is a lateral view of the lumbar vertebra of FIG. 16A, with bonefiller injected into the vertebra;

FIG. 16C is a lateral view of the lumbar vertebra of FIG. 16B, with acavity-forming device inserted into the vertebra;

FIG. 16D is a lateral view of the lumbar vertebra of FIG. 16C, with thecavity-forming device expanded in the cavity;

FIG. 17 is a side view of a cavity-forming device constructed inaccordance with another alternate embodiment of the present invention;

FIG. 18 is a side view of a cavity-forming device constructed inaccordance with another alternate embodiment of the present invention;

FIG. 19 is a cross-sectional view of the cavity-forming device of FIG.18, taken along line 19-19; and

FIG. 20 is a cross-sectional view of the cavity-forming device of FIG.18, taken along line 20-20.

DESCRIPTION OF THE INVENTION

As embodied and broadly described herein, the present invention isdirected to surgical methods for repairing, reinforcing and/or treatingweakened, diseased and/or fractured bone. The present invention isfurther directed to various devices for facilitating such surgicalmethods.

FIG. 1 depicts a typical human spine 1, in which a compression fracture10 has occurred in a lumbar vertebra 100. As best shown in FIG. 3,vertebra 100 has fractured, with the top and bottom plates 103 and 104depressing generally towards the anterior wall 10 of the vertebra 100and away from their pre-fracture, normally parallel orientation(indicated generally as parallel lines 90).

FIG. 4 depicts a coronal (top) view of the vertebra of FIG. 3. Vertebra100 includes a vertebral body 105, which extends on the anterior (i.e.front or chest) side of the vertebra 100. Vertebral body 105 isapproximately the shape of an oval disk, with an anterior wall 10 and aposterior wall 261. The geometry of the vertebral body 105 is generallysymmetric. Vertebral body 105 includes an exterior formed from compactcortical bone 110. The cortical bone 110 encloses an interior volume ofreticulated cancellous, or spongy, bone 115 (also called medullar boneor trabecular bone).

The spinal canal 150 is located on the posterior (i.e. back) side ofeach vertebra 100. The spinal cord 151 passes through the spinal canal150. A vertebral arch 135 surrounds the spinal canal 150. Left and rightpedicles 120 of the vertebral arch 135 adjoin the vertebral body 105.The spinous process 130 extends from the posterior of the vertebral arch135, as do the left and right transverse processes 125 and the mamillaryprocesses 126.

FIG. 2 depicts a patient 50 prepared for disclosed methods of thepresent invention. These procedures can be performed on an outpatient orinpatient basis by a medical professional properly trained and qualifiedto perform the disclosed procedures. Desirably, the patient will beplaced under general or local anesthetic for the duration of thesurgical procedures.

In one embodiment of the present invention, a surgical method comprisesinserting an insertion device 350 (see FIG. 5A) percutaneously into thebone, such as a fractured vertebral body 105 through, preferably, atargeted area of the back, depicted as 60 in FIG. 2. The insertiondevice 350 may be any type and size of hollow instrument, preferablyhaving a sharp end. In one preferred embodiment, the insertion device350 comprises a hollow needle of approximately eleven gauge diameter. Aneleven gauge needle is preferred for the procedure because itincorporates a hollow lumen of sufficient size to permit the passage ofvarious instruments and materials, yet the overall size of the needle issmall enough to minimize bone and tissue damage in the patient. Itshould be understood, however, that various other size needleassemblies, including needles of six to 14 gage, could be used with thedevices and methods of the present invention, with varying results. Inaddition, various other access instruments, such as those described inU.S. Pat. Nos. 4,969,888, 5,108,404, 5,827,289, 5,972,015, 6,048,346 and6,066,154, each of which are incorporated herein by reference, could beused in accordance with the teachings of the present invention, withvarying results.

The insertion device 350 is preferably comprised of a strong,non-reactive, and medical grade material such as surgical steel. Ifdesired, the insertion device 350 is attached to a manipulating assemblywhich is comprised of a non-reactive and medical grade materialincluding, but not limited to, acrylonitrile-butadiene-styrene (ABS),polyethylene, polypropylene, polyurethane, Teflon, or surgical steel.FIG. 5A depicts a commercially available needle assembly typically usedwith various embodiments of the present invention, which are furtherdescribed below.

As shown in FIG. 5A, an insertion device 350, such as an eleven gaugebiopsy needle (commercially available from Becton Dickinson & Co ofFranklin Lakes, N.J.) can be inserted through soft tissues of the backand into the vertebral body 105. Generally, the approach for such aprocedure will be transpedicular, although various other approaches,including lateral, extrapedicular and/or anterior approaches, could beused, depending upon the level treated and/or intervening anatomicalfeatures well known to those of ordinary skill in the art. In oneembodiment, the device 350 comprises a needle body 348 and a stylet 349,as is well known in the art. During insertion of the device 350, thelocation of the device 350 is desirably monitored using visualizationequipment such as real-time X-Ray, CT scanning equipment 70 (see FIG.2), MRI, or any other monitoring equipment commonly used by those ofskill in the art, including computer aided guidance and mappingequipment such as the systems commercially available from BrainLabCorporation or General Electric Corporation.

In one preferred embodiment, the distal end 351 of the insertion device350 is positioned in the vertebral body 105, preferably at a locationtowards the posterior side of the vertebral body 105. If desired, thedistal end 351 could be positioned in various locations throughout thevertebral body 105, including towards the anterior side. Once inposition, the stylet 349 of the insertion device 350 may be removed, seeFIG. 5B, and a cavity-forming device 200 may be inserted through theshaft 348 and into the vertebral body 105. See FIG. 5C. Thecavity-forming device 200, which is desirably comprised of abiologically compatible and medically acceptable material, can be asmall mechanical tamp, reamer, hole punch, balloon catheter (asdescribed below) or any appropriate device which is capable ofdisplacing cancellous bone. Once the cavity-forming device is positionedwithin the vertebral body 105, it is used to displace cancellous bone115, thereby creating a cavity 170. See FIG. 5F.

In one embodiment, shown in FIGS. 9 and 10, the cavity-forming devicecomprises a balloon catheter 200. The balloon catheter 200 desirablyextends across at least 20% of the vertebral body, but could extendgreater or lesser amounts, depending upon the desired size of the cavityto be produced. In this embodiment, as the balloon catheter 201 isexpanded, cancellous bone is displaced generally outward from the cavity170 in a controlled manner, desirably forming a compressed-bone region172 around a substantial portion of the outer periphery of the cavity170.

The balloon catheter 200, which will be described in more detail below,is sized or folded to fit through the hollow interior of the shaft 348and into a vertebral body 105. Once in a desired position within thevertebral body 105, the balloon catheter 190 is filled with apressurized filling medium 275 appropriate for use in medicalapplications including, but not limited to, air, nitrogen, saline orwater. See FIGS. 5D and 11. In a preferred embodiment, the fillingmedium 275 is a radiopaque fluid (such as Conray® fluid availablecommercially from Mallinkrodt, Inc., of St. Louis, Mo.), which allowsthe physician to visualize the catheter 190 during inflation. Ifdesired, alternate ways of expanding the catheter, including mechanicalexpanders, jacks, expanding springs and/or expanding/foaming agents,could be used, with varying results.

In one embodiment, the catheter 201 is expanded to any appropriatevolume which creates a cavity 170 within the vertebral body 105. In apreferred embodiment, the catheter 201 is expanded to at least 0.20 ccin volume, but could be expanded to significantly greater sizes, such as1, 2, 4, 6 or 8 cc, depending upon bone quality and density. Aftercavity creation, the catheter 201 is deflated (see FIG. 5E) and removedfrom the vertebral body 105 and shaft 348 (see FIG. 5F). Bone filler 180is introduced through the shaft 348 and into the vertebral body 105using any type of plunger, extruder and/or feed line assembly 349compatible with the needle body 348. Once injection of bone filler iscomplete, the shaft 348 can be withdrawn.

If desired, a portion of the balloon catheter 201 could be temporarilyor permanently left within a vertebral body 105. For example, aftercavity formation and removal of the inflation medium, the deflatedexpanded section of the balloon catheter 201 could be refilled with bonefiller 180 and left within the vertebral body 105. Alternatively, theinflation medium 275 could comprise bone filler 180. After the ballooncatheter 201 is filled with such an inflation medium, at least a portionof the catheter 201 could be left permanently within the cavity 170. Inan alternate embodiment, the catheter 201 which is intended to remainwith the cavity 170 could comprise a bio-absorbable material and/orfabric/mesh material as the expandable structure.

In creating the cavity 170, the inflation of the catheter 201 causes theexpandable material 210 to press against the cancellous bone 115 whichmay form a compressed bone region or “shell” 172 along much of theperiphery of the cavity 170. This shell 172 will desirably inhibit orprevent bone filler 180 from exiting the cavity 170, thereby inhibitingextravazation of the bone filler and/or facilitating pressurization ofthe bone filler 180, if desired, within the cavity. As the pressure inthe cavity 170 increases, the walls of the cavity 170 will desirably beforced further outward by the bone filler 180, compressing additionalcancellous bone within the vertebral body 105 and/or increasing the sizeof the cavity 170. If sufficient pressure is available, and integrity ofthe shell 172 can be maintained without significant leakage of bonefiller 180, pressures capable of moving fractured cortical bone can bedeveloped.

In one embodiment of the present invention, after cavity formation, anamount of a material, such as a bone filler 180, is introduced throughthe shaft 348 into the vertebral body 105 under low pressure. The amountof bone filler will desirably be more than the volume of the cavity 170,however, less bone filler may be introduced with varying results. Oncethe cavity 170 is substantially filled, the continued introduction ofbone filler 180 will desirably pressurize the bone filler 180 in thecavity 170 such that the increased pressure will cause at least aportion of the walls of the cavity to move outward, thereby enlargingthe cavity 170 and. further compressing cancellous bone and/or movingcortical bone. Desirably, introduction of the bone filler 180 willcontinue until bone filler leak from the vertebral body appearsimminent, the cortical bone has regain its pre-fractured position and/orthe practitioner determines that sufficient bone filler 180 has beeninjected into the bone. If desired, the physician can utilize thecavity-forming device to create additional cavities for bone filler, orthe shaft 348 can be removed from the vertebral body to completed theprocedure.

The bone filler 180 could be any appropriate filling material used inorthopedic surgery, including, but not limited to, allograft orautograft tissue, hydroxyapatite, epoxy, PMMA bone cement, or syntheticbone substitutes such Osteoset® from Wright Medical Technology, medicalgrade plaster of paris, Skeletal Repair System (SRS®) cement from NorianCorporation, or Collagraft from Zimmer. As bone filler 180 is introducedinto the vertebral body 105, the introduction is desirably monitored byx-ray fluoroscopy, or any other appropriate monitoring device or method,to ensure that bone filler 180 does not flow outside of the vertebralbody 105. To facilitate visualization, the bone filler 180 may be mixedwith a fluoroscopic agent, such as radio opaque barium sulfate. Inanother embodiment, the bone filler 180 could comprise a mixture of bonecement and a thixotropic material which desirably limits and/or preventsextravazation of the bone cement.

In an alternate embodiment of the disclosed method, shown in FIGS. 5Gthrough 5L, a first bone filler 180 is introduced into the cavity 170,the amount of first bone filler 180 being desirably less than orapproximately equal to the volume of the cavity 170. For example, if theballoon catheter 200 utilized to create the cavity 170 was inflated with1.0 cc of inflation fluid, then less than or approximately 1.0 cc ofbone filler 180 will initially be injected into the cavity 170. Ofcourse, if desired, an amount of first bone filler 180 greater than thecavity volume could be injected into the cavity. The shaft 348 is thenre-positioned within the vertebral body 105, see FIG. 5H, with thedistal end 351 of the device 350 desirably located within the bolus 400of first bone filler 180 contained in the cavity 170. As best shown inFIG. 5I, a second amount of bone filler 182 is then injected into thevertebral body 105, which desirably forces the first amount of bonefiller 180 outward against the walls of the cavity 170. Desirably, thefirst amount of bone filler 180 will resist extravazating out of thecavity 170 and will push outward against the walls of the cavity 170,further compressing the cancellous bone 115 and/or increasing the sizeof the cavity 170. Introduction of the second amount of bone filler 182will desirably continue until bone filler leak from the vertebral bodyappears imminent, the cortical bone has regained its pre-fracturedposition, and/or the practitioner determines that sufficient bone filler180 has been injected into the bone. If desired, the physician couldreinsert a catheter 200 to create an additional cavity, or the shaft 348can be removed to complete the procedure.

FIGS. 8A through 8C depict an alternate embodiment of the disclosedmethod, in which the practitioner introduces a first material, such as abone filler 180, into the cavity 170, and subsequently inserts acavity-forming device 200 into the bone. The cavity-forming device 200is then expanded, and desirably compresses the bone filler 180 againstthe walls of the cavity, sealing any significant cracks and/or venouspassages through which the cement will flow. In one further embodiment,a practitioner may wait to allow the first bone filler to hardenpartially or fully prior to removing the cavity-forming device and/orprior to introducing a second material, such as a bone filler. Thesecond material (not shown) can subsequently be injected into thevertebral body with little fear of leakage. If desired, this methodcould be utilized whenever cement leakage appears imminent, and can berepeated multiple times until the practitioner determines thatsufficient bone filler 180 has been injected into the bone. In addition,the practitioner could repeat this procedure until the cortical bone hasregained its pre-fractured position. In an alternate embodiment, thepractitioner could utilize a cavity-forming device prior to theintroduction of the first bone filler, and then introduce the first bonefiller into the cavity, subsequently follow one or more of the describedmethods.

The first bone filler will desirably comprise a material that can beintroduced into the cavity, but which will resist extravazation out ofthe cavity and/or vertebral body when the second bone filler is injectedinto the cavity. In one embodiment of the invention, the first andsecond bone fillers comprise bone cement, with the first bone cementbeing more resistant to extravazation than the second bone cement. Forexample, the ingredients of the first bone cement could be specificallytailored such that the first bone cement cures faster than the secondbone cement. Alternatively, the first bone cement could be preparedand/or introduced into the vertebral body before the second bone cement,allowing the first bone cement to partially or fully cure before thesecond bone cement. Alternatively, the curing and/or hardening of thefirst bone cement could be accelerated (by applying heat, for example)or curing and/or hardening of the second bone cement could be retarded(by cooling, for example). In another embodiment, the first and secondbone fillers comprise bone cement, with the first bone cement desirablybeing more viscous than the second bone cement. In another alternateembodiment, the first bone filler comprises an expandable structure,such as a stent.

In another embodiment, the first bone filler comprises a material moreviscous than the second bone filler, the first and second bone fillerscomprising different materials. In another embodiment, the first bonefiller comprises a material which is more resistant to extravazationinto the cancellous bone than the second bone filler. In anotherembodiment, the first bone filler comprises a material having particlesgenerally larger than particles in the second bone filler. In a furtherembodiment, the particles of the first bone filler are generally largerthan the average pore size within the cancellous bone. In anotherembodiment, the first bone filler comprises a settable material, such asa two-part polyurethane material or other curable bio-material.

FIGS. 16A through 16D depict an alternate embodiment of the disclosedmethod, in which a first material, such as a bone filler 180, isinitially introduced into the cancellous bone 115 of a human bone, suchas a vertebral body 105. An expandable structure 210, such as that foundat the distal end of a balloon catheter 200, is subsequently insertedinto the vertebral body 105. The expandable structure 210 is thenexpanded, which displaces the bone filler 180 and/or cancellous bone115, creating a cavity 170 within the vertebral body 105. In oneembodiment, the expansion of the expandable structure 210 forces thebone filler 180 further into the cancellous bone 115, and/or furthercompresses cancellous bone. To minimize bone filler 180 leakage, thebone filler may be allowed to partially or completely harden prior toexpansion of the expandable structure 210. Alternatively, the expandablestructure 210 may be expanded, and the bone filler 180 allowed topartially or completely harden around the expandable structure 210. Ineither case, a second material, optionally additional bone filler, maybe introduced into the cavity 170. In one embodiment, the secondmaterial is a material which supports the bone in a resting position.This method may be utilized whenever cement leakage appears imminent,and may be repeated multiple times until the practitioner determinesthat sufficient amounts and varieties of material have been introducedinto the bone. Alternatively, the practitioner could halt introductionof filler material when the cortical bone regains or approximates itspre-fractured position.

By creating cavities and/or preferred flowpaths within the cancellousbone, the present invention obviates the need for extremely highpressure injection of bone filler into the cancellous bone. If desired,the bone filler could be injected into the bone at or near atmosphericand/or ambient pressures, or at pressures less than approximately 400pounds per square inch, using bone filler delivery systems such as thosedescribed in co-pending U.S. patent application Ser. No. 09/134,323,which is incorporated herein by reference. Thus, more viscous bonefillers (such as, for example, thicker bone cement) can be injected intothe bone under low pressures (such as, for example, exiting the deliverydevice at a delivery pressure at or near ambient or atmosphericpressure), reducing opportunities for cement leakage and/orextravazation outside of the bone.

Cavity-Forming Devices

The present invention also includes cavity-forming devices constructedin accordance with the teachings of the disclosed invention. In oneembodiment, the cavity-forming device comprises a balloon catheter 201,as shown in FIGS. 9, 10, and 11. The catheter comprises a hollow tube205, which is desirably comprised of a medical grade material such asplastic or stainless steel. The distal end 206 of the hollow tube 205 issurrounded by an expandable material 210 comprised of a flexiblematerial such as commonly used for balloon catheters including, but notlimited to, metal, plastics, composite materials, polyethylene, mylar,rubber or polyurethane. One or more openings 250 are disposed in thetube 205 near the distal end 206, desirably permitting fluidcommunication between the hollow interior of the tube 205 and the lumenformed between the tube 205 and the expandable structure 210. A fitting220, having one or more inflation ports 222, 224, is secured to theproximal end 207 of the tube 205. In this embodiment, once the catheter201 is in its desired position within the vertebral body 105, aninflation medium 275 is introduced into the fitting 220 through theinflation port 222, where it travels through the fitting 220, throughthe hollow tube 205, through the opening(s) 250 and into the lumen 274between the expandable structure 210 and the hollow tube 205. Asinjection of the inflation medium 275 continues, the pressure of theinflation medium 275 forces the expandable structure 210 away from thehollow tube 205, inflating it outward and thereby compressing cancellousbone 115 and forming a cavity 170. Once a desired cavity size isreached, the inflation medium 275 is withdrawn from the catheter 200,the expandable structure collapses within the cavity 170, and thecatheter 200 may be withdrawn.

For example, a balloon catheter 201 constructed in accordance with onepreferred embodiment of the present invention, suitable for use with an11-gauge needle, would comprise a hollow stainless steel hypodermic tube205, having an outer diameter of 0.035 inches and a length of 10.75inches. One or more openings 250 are formed approximately 0.25 inchesfrom the distal end of the tube 205. In a preferred embodiment, thedistal end 206 of the hollow tube 205 is sealed closed using any meanswell known in the art, including adhesive (for example, UV 198-Madhesive commercially available from Dymax Corporation—cured forapproximately 15 minutes under UV light).

In one embodiment, the hollow tube 205 is substantially surrounded by anexpandable structure 210 comprising an extruded tube of polyurethane(for example, TEXIN® 5290 polyurethane, available commercially fromBayer Corporation). In one embodiment, the polyurethane tube has aninner diameter of 0.046 inches, an outer diameter of 0.082 inches, and alength of 9½ inches. The distal end of the polyurethane tube is bondedto the distal end 206 of the hollow tube 205 by means known in the art,such as by a suitable adhesive (for example, UV 198-M adhesive).Alternatively, the polyurethane tube may be heat sealed about the distalend 206 of the hollow tube 205 by means well known in the art. A ¾ inchlong piece of heat shrink tubing 215 (commercially available fromRaychem Corporation) , having a 3/16 inch outer diameter, may be securedaround the proximal end of the polyurethane tubing. In one embodiment,the proximal end of the hollow tubing 205 is inserted into the fitting220 and the heat shrink tubing 215 is desirably bonded into the fitting220 using a suitable adhesive known in the art, such as UV 198-M. Thefitting 220, which may be a Luer T-fitting, commercially available fromnumerous parts suppliers, may be made of any appropriate material knownto those of skill in the art. The fitting 220 comprises one or moreports 222, 224 for attachment to additional instruments, such as pumpsand syringes (not shown). If desired, the hollow tube 205 can similarlybe bonded into the fitting 220 using a suitable adhesive. Alternatively,as shown in FIG. 12, the expandable structure 210 could be significantlyshorter than the hollow tube 205 and be bonded at its distal end 206 andits proximal end 209 to the hollow tube 205.

The hollow tube 205 and one or more openings 250 facilitate thewithdrawal of inflation medium from the catheter during the disclosedprocedures. When a catheter is deflated, the expandable structure 210will normally collapse against the tube 205, which can often seal closedthe lumen (in the absence of at least one secondary withdrawal path) andinhibit further withdrawal of inflation medium from the expandedstructure 210 of a catheter. However, in an embodiment of the disclosedinvention, the one or more openings 250 near the distal end of the tube205 allow inflation medium 275 to be drawn through the hollow hypodermictube 205, further deflating the expandable structure 210. The strongwalls of the hollow hypodermic tube 205 resist collapsing under thevacuum which evacuates the inflation medium, maintaining a flowpath forthe inflation medium and allowing the inflation medium to be quicklydrawn out of the catheter, which desirably permits deflation of thecatheter in only a few seconds.

In the disclosed embodiment, as the catheter 201 is inflated, theinflation medium 275 will typically seek to fill the entire lumenbetween the expandable structure 210 and the hollow tube 205, thusexpanding the catheter 201 along the entire length of the expandablestructure 210. However, because much of the catheter 201 is locatedwithin the lumen of the shaft 348, with the distal end 206 of thecatheter 201 extending into the vertebral body 105, the shaft 348 willdesirably constrain expansion of the expandable structure 210, causingthe expandable structure 210 to expand primarily at the distal end 206of the catheter 200. Desirably, further insertion or withdrawal of thecatheter 201 will alter the amount of the expandable structure 210extending from the distal end of the shaft 348, thereby increasing ordecreasing the length of the expandable structure 210 that is free toexpand within the vertebral body 105. By choosing the amount of catheter201 to insert into the vertebral body 105, the practitioner can alterthe length of the expandable structure, and ultimately the size of thecavity 170 created by the catheter 201, during the surgical procedure.Therefore, the disclosed embodiments can obviate and/or reduce the needfor multiple catheters of varying lengths. If desired, markings 269 (seeFIG. 9) can be placed along the proximal section of the catheter whichcorrespond to the length of the catheter 201 extending from the shaft348, allowing the practitioner to gauge the size of the expandablestructure 210 of the catheter 200 within the vertebral body 105.Similarly, in an alternate embodiment as disclosed below, thecavity-forming device 201 could incorporate markings corresponding tothe length of the bristles 425 extending beyond the tip of the shaft348.

In an alternate embodiment, shown in FIG. 13, the length of anexpandable section 211 of the catheter can be further constrained bysecuring and/or adhering the expandable structure 210 at a secondarylocation 214 along the hollow tube 205, thereby limiting expansionbeyond the secondary location 214. For example, if a desired maximumlength of the expandable section 211 were 3 inches, then the expandablestructure 210 could be secured to the hollow tube 205 at a secondarylocation 214 approximately three inches from the distal end 206 of thehollow tube 205. This arrangement would desirably allow a practitionerto choose an expanded length of the expandable section 211 of up tothree inches, while limiting and/or preventing expansion of theremaining section 203 of the catheter 201. This arrangement can alsoprevent unwanted expansion of the portion 202 of the catheter extendingout of the proximal end 191 of the shaft body 348 (see FIG. 5C).

As previously noted, in the disclosed embodiment, the expandablestructure is desirably secured to the distal end of the hollow tube,which will facilitate recovery of fragments of the expandable structure210 if the expandable structure 210 is torn or damaged, such as by acomplete radial tear. Because the hollow tube 205 will desirably remainattached to the fragments (not shown) of the expandable structure 210,these fragments can be withdrawn from the vertebral body 105 with thehollow tube 205. In addition, the distal attachment will desirablyprevent and/or reduce significant expansion of the expandable structure210 along the longitudinal axis of the hollow tube 205.

FIG. 17 depicts a cavity-forming device 300 constructed in accordancewith an alternate embodiment of the present invention. Because many ofthe features of this embodiment are similar to embodiments previouslydescribed, like reference numerals will be used to denote likecomponents. In this embodiment, the hollow tube 205 extends through thefitting 220, such as a t-shaped fitting, and is secured to a cap 310. Ina preferred embodiment, the hollow tube 205 is capable of rotationrelative to the fitting 220. If desired, a seal (not shown), such as asilicone or teflon o-ring, can be incorporated into the proximal fitting222 to limit and/or prevent leakage of inflation medium past the hollowtube 205.

In use, a cavity-forming device 300 compresses cancellous bone and/orforms a cavity in a manner similar to the embodiments previouslydescribed. However, once the cavity is formed and withdrawal of thedevice 300 is desired, the cap 310 can be rotated, twisting theexpandable material 210 relative to the fitting 220 and drawing theexpandable structure 210 against the hollow tube 205, desirablyminimizing the overall outside diameter of the expandable portion of thedevice 300. The device 300 can then easily be withdrawn through theshaft 348. Even where the expandable structure 210 has plasticallydeformed, or has failed in some manner, the present embodiment allowsthe expandable structure 210 to be wrapped around the hollow tube 205for ease of withdrawal and/or insertion. Alternatively, the hollow tube205 may be capable of movement relative to the longitudinal axis of thefitting 220, which would further stretch and/or contract the expandablestructure 210 against the hollow tube 205.

FIGS. 6A and 6B depict a cavity-forming device 410 constructed inaccordance with an alternate embodiment of the present invention.Cavity-forming device 410 comprises a shaft 420 which is desirably sizedto pass through the shaft 348 of an insertion device 350. A handleassembly 415, which facilitates manipulation of the cavity-formingdevice 410, is secured to the proximal end 412 of the shaft 420. One ormore wires or “bristles” 425 are secured to the distal end 423 of theshaft 420. The bristles 425 can be secured to the shaft 420 by welding,soldering, adhesives or other securing means well known in the art.Alternatively, the bristle(s) 425 can be formed integrally with theshaft 420, or can be etched from a shaft using a laser or other meanswell known in the art. The bristles and shaft may be formed of a strong,non-reactive, and medical grade material such as surgical steel. In oneembodiment, the bristles 425 extend along the longitudinal axis of theshaft 425, but radiate slightly outward from the shaft axis. In thismanner, the bristles 425 can be collected or “bunched” to pass throughthe shaft 348, but can expand or “fan” upon exiting of the shaft 348. Ifdesired, the bristles can be straight or curved, to facilitate passagethrough the cancellous bone 115. In addition, if desired, one or more ofthe bristles 425 may be hollow, allowing a practitioner to take a biopsysample of the cancellous bone during insertion of the device 410.

As shown in FIG. 7, the cavity-forming device 410 can desirably beinserted through a shaft 348 positioned in a targeted bone, such as avertebral body 105. As the bristles 425 enter the cancellous bone 115,the bristles 425 will desirably displace the bone 115 and create one ormore cavities 426 or preferred flowpaths in the vertebral body. Ifdesired, a practitioner can withdraw the bristles 425 back into theshaft 348, reposition the cavity-forming device 410 (such as by rotatingthe device 410), and reinsert the bristles 425, thereby creatingadditional cavities in the cancellous bone 115. After removal of thecavity-forming device 410, a material, such as a bone filler, (notshown), may be introduced through the shaft 348. The bone filler willdesirably initially travel through the cavities 426 created by thebristles 425. If desired, a practitioner may interrupt introduction ofthe bone filler and create additional cavities by reinserting thecavity-forming device 410. In addition, in the event bone filler leakageoccurs or is imminent, a practitioner can interrupt bone fillerinjection, create additional cavity(ies) as described above, wait forthe introduced/leaking bone filler to harden sufficiently to resistfurther extravazation, and then continue introduction of bone filler. Aspreviously described, the bone filler could comprise many differentmaterials, or combinations of materials, with varying results.

FIG. 14 depicts a cavity-forming device 500 constructed in accordancewith an alternate embodiment of the present invention. Thecavity-forming device 500 comprises a shaft 520 which is sized to passthrough the shaft 348 of an insertion device 350. A handle assembly 515,which facilitates manipulation of the cavity-forming device 500, issecured to the proximal end 512 of the shaft 520. The shaft 520 of thecavity-forming device 500 is desirably longer than the shaft 348 of theinsertion device 350. The distal end 525 of the shaft 520 can be beveled(not shown) to facilitate passage through cancellous bone 115, or can berounded or flattened to minimize opportunities for penetrating theanterior wall 10 of the vertebral body 105. In addition, if desired, thedistal 525 end of the shaft 520 could be hollow (not shown), allowingthe practitioner to take a biopsy sample of the cancellous bone 115during insertion of the device 500.

FIG. 15 depicts a cavity-forming device 600 constructed in accordancewith an alternate embodiment of the present invention. Cavity-formingdevice 600 comprises a shaft 620 which is sized to pass through theshaft 348 of an insertion device 350. A handle assembly 615, whichfacilitates manipulation of the cavity-forming device 600, is secured tothe proximal end 612 of the shaft 620. The shaft 620 is desirably longerthan the shaft 348 of insertion device 350. The distal end 625 of theshaft 620 can be beveled (not shown) to facilitate passage throughcancellous bone 115, or can be rounded or flattened to minimizeopportunities for penetrating the anterior wall 10 of the vertebral body105. In this embodiment, the distal end 625 of the device 600incorporates drill threads 627 which can facilitate advancement of thedevice 600 through cancellous bone 115. In addition, if desired, thedistal 625 end of the shaft 620 could be hollow, allowing thepractitioner to take a biopsy sample of the cancellous bone 115 duringinsertion of the device 600.

After removal of the device(s), bone filler (not shown) may beintroduced through the shaft 348. Desirably, the bone filler willinitially travel through the cavity(ies) created by the device(s). Ifdesired, a practitioner can interrupt introduction of bone filler andcreate additional cavity(ies) by reinserting the device(s). In addition,in the event bone filler leakage occurs or is imminent, the practitionercan interrupt bone filler introduction, create additional cavity(ies) asdescribed above, wait for the introduced/leaking bone filler to hardensufficiently, and then continue introducing bone filler. As previouslydescribed, the bone filler could comprise many different materials, orcombinations of materials, with varying results.

FIGS. 18-20 depicts a cavity-forming device 600 a constructed inaccordance with another alternate embodiment of the present invention.Because many of the components of this device are similar to thosepreviously described, similar reference numerals will be used to denotesimilar components. Cavity-forming device 600 a comprises a shaft 620 awhich is sized to pass through the shaft 348 of an insertion device 350.A handle assembly 615 a, which facilitates manipulation of thecavity-forming device 600 a, is secured to the proximal end 612 a of theshaft 620 a. The shaft 620 a is desirably longer than the shaft 348 ofinsertion device 350. The distal end 625 a of the shaft 620 a can berounded or beveled to facilitate passage through cancellous bone 115, orcan be or flattened to minimize opportunities for penetrating theanterior wall 10 of the vertebral body 105.

An opening or window 700 is desirably formed in the shaft 620 a. Asshown in FIGS. 19 and 20, an expandable structure 710 is located atleast partially within the shaft 620 a, desirably at a position adjacentthe window 700. Upon introduction of inflation fluid through a lumenextending through the shaft 620 a, the expandable structure 710 expandsand at least a portion of the expandable structure 710 will extend outof the shaft 620 a through the window 700. Desirably, as the structurecontinues to expand, the expandable structure 710 will “grow” (P1 to P2to P3 in FIG. 20) through the window 700, thereby compacting cancellousbone, creating a cavity and/or displacing cortical bone. Uponcontraction of the expandable structure 710, most of the expandablestructure 710 will desirably be drawn back into the shaft 620 a forremoval of the tool from the vertebral body. In one embodiment, at leasta portion of the material comprising the expandable structure 710 willplastically deform as it expands.

The expandable structure 710 may be comprised of a flexible materialcommon in medical device applications, including, but not limited to,plastics, polyethylene, mylar, rubber, nylon, polyurethane, metals orcomposite materials. Desirably, the shaft 620 a will comprise a materialthat is more resistant to expansion than the material of the expandablestructure 710, including, but not limited to, stainless steel, ceramics,composite material and/or rigid plastics. In an alternate embodiment,similar materials for the expandable structure 710 and shaft 620 a maybe used, but in different thickness and/or amounts, thereby inducing theexpandable structure to be more prone to expansion than the shaft 620 amaterial. The expandable structure 710 may be bonded directly to theshaft 620 a by various means well known in the art, including, but notlimited to, means such as welding, melting, gluing or the like. Inalternative embodiments, the expandable structure may be secured insideor outside of the shaft 620 a, or a combination thereof.

As previously noted, any of the cavity-forming devices 500, 600 and 600a may be inserted through a shaft 348 positioned in a targeted bone,such as a vertebral body 105. As the device(s) enter the cancellous bone115, they will desirably displace the bone 115 and create one or morecavities in the vertebral body. If desired, the physician can withdrawthe device(s) back into the shaft 348 and reinsert as necessary tocreate the desired cavity(ies) in the cancellous bone 115.

In the embodiment of a cavity-forming device of FIGS. 18-20, thecavity-forming device 600 a may be utilized without an associatedinsertion device. In such a case, the cavity-forming device desirablywill incorporate a sharpened distal tip capable of penetrating the softtissues and cortical/cancellous bone of the vertebral body. If desired,the distal tip can be hollow or a solid construct. Similarly, the windowmay extend around more or less of the periphery of the shaft 620 a,depending upon the size and configuration of the expandable structureand the desired strength of the cavity-forming device.

By creating one or more cavities within the cancellous bone 115, thecavity-forming devices of the present invention desirably createpreferred flowpaths for the bone filler 180. In addition, thecavity-forming devices can also desirably close and/or block othernatural flowpaths out of the cavity, such as veins and/or cracks in thecancellous bone. Moreover, methods and devices disclosed herein can beused to manipulate bone filler already introduced into the bone. Thus,the present invention reduces opportunities for cement leakage outsideof the vertebral body and/or improves the distribution of bone fillerthroughout significant portions of the vertebral body. In addition, thecreation of cavities and desired flowpaths described in the presentinvention permits the placement of biomaterial more safely, undergreater control and under lower pressures.

In addition to the specific uses described above, the cavity-formingdevices and methods described herein would also be well-suited for usein treating and/or reinforcing weakened, diseased and/or fractured bonesand other organs in various locations throughout the body. For example,the disclosed devices and methods could be used to deliver reinforcingmaterials and/or medications, such as cancer drugs, replacement bonecells, collagen, bone matrix, demineralized calcium, and othermaterials/medications, directly to a fractured, weakened and/or diseasedbone, thereby increasing the efficacy of the materials, reinforcing theweakened bone and/or speed healing. Moreover, injection of suchmaterials into one bone within a body could permit themedication/material to migrate and/or be transported to other bonesand/or organs in the body, thereby improving the quality of bones and/orother organs not directly injected with the materials and/ormedications.

Other embodiments and uses of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. All documents referenced herein arespecifically and entirely incorporated by reference. The specificationand examples should be considered exemplary only with the true scope andspirit of the invention indicated by the following claims. As will beeasily understood by those of ordinary skill in the art, variations andmodifications of each of the disclosed embodiments can be easily madewithin the scope

1.-5. (canceled)
 6. A method, comprising: introducing a first amount ofbone cement into a cavity defined within cancellous bone within avertebral body; and introducing a second amount of bone cement into thecavity of the vertebral body after the introducing the first amount ofbone cement, such that a distance between a first end plate and a secondend plate of the vertebral body are substantially unchanged after theintroducing the first amount of bone cement and the distance beingincreased after the introducing the second amount of bone cement.
 7. Themethod of claim 6, wherein at least a portion of the cancellous bone iscompressed by the introducing the first amount of bone cement, and 8.The method of claim 6, wherein: the introducing the first amount of bonecement includes using a plunger to displace the first amount of bonecement, and the introducing the second amount of bone cement includesusing the plunger to displace the second amount of bone cement.
 9. Themethod of claim 6, wherein the bone cement has particles larger than apore size within the cancellous bone.
 10. The method of claim 6, whereinthe introducing the first amount of bone cement includes introducing thefirst amount of bone cement percutaneously.
 11. The method of claim 6,wherein the introducing the first amount of bone cement includesintroducing a settable material.
 12. The method of claim 6, furthercomprising first inserting percutaneously an elongate body into thevertebral body to create the cavity.
 13. The method of claim 6, whereinthe introducing the first amount of bone cement and the introducing thesecond amount of bone cement occurs substantially without leakage of thebone cement from the cavity.
 14. A method, comprising: inserting anelongate body into an interior of a vertebral body; inserting a firstamount of bone cement into a cavity defined within the vertebral body, adistance between a first end plate of the vertebral body and a secondend plate of the vertebral body being substantially unchanged after theinserting the first amount of bone cement; and inserting a second amountof bone cement into the interior of the vertebral body, the distancebetween the first end plate and the second end plate of the vertebralbody being substantially restored after the inserting the second amountof bone cement.
 15. The method of claim 14, wherein the inserting thefirst amount of bone cement and the inserting the second amount of bonecement occurs substantially without leakage of the bone cement from thecavity.
 16. The method of claim 14, wherein the elongate body has atapered distal end.
 17. The method of claim 14, wherein the insertingthe elongate body includes inserting the elongate body percutaneously.18. The method of claim 14, wherein the elongate body has a distal endportion including an expandable portion, the expandable portion having acollapsed configuration and an expandable configuration.
 19. The methodof claim 14, further comprising: monitoring fluoroscopically theinterior of the vertebral body during the inserting the second amount ofbone cement.
 20. The method of claim 14, wherein the inserting the firstamount of bone cement includes injecting the bone cement at atmosphericpressure.
 21. The method of claim 14, the elongate body being introducedinto the interior of the vertebral body through a shaft, the methodfurther comprising: removing the elongate body through the shaft beforethe inserting the first amount of bone cement into the cavity, the bonecement being introduced through the shaft.
 22. A kit, comprising: anelongate body configured to be introduced into an interior of avertebral body to define a cavity in cancellous bone; a plungerconfigured to be coupled to the elongate body; a first amount of bonecement such that a distance between a first end plate and a second endplate of the vertebral body is substantially unchanged when the firstamount of bone cement is inserted into the interior of the vertebralbody via the plunger and the elongate body; and a second amount of bonecement sufficient to increase the distance between the first end plateand the second end plate of the vertebral body when inserted into theinterior of the vertebral body via the plunger and the elongate body.23. The kit of claim 22, wherein: a distal end portion of the elongatebody has an expandable portion, the expandable portion having acollapsed configuration and an expandable configuration, the distal endportion of elongate body being configured to be introduced into theinterior of the vertebral body while in the collapsed configuration, andthe distal end portion of the elongate body configured to define thecavity while in the expanded configuration.
 24. The kit of claim 22,wherein: the bone cement has particles larger than a pore size withinthe cancellous bone.
 22. A method, comprising: inserting a bone cementinto a vertebral body, a distance between a first end plate of thevertebral body and a second end plate of the vertebral body beingsubstantially changed after the inserting the bone cement.